1. Field of the Invention
The present invention relates to a microcomputer using, for example, memories of N (8) bit data width as a single memory of N.times.M (16) bit data width and a method of determining completion of writing in the microcomputer.
2. Description of the Related Art
Generally, a microcomputer has a built-in mask ROM in which a program for operation control is stored, or a built-in RAM in which data are stored. Further, a nonvolatile memory (flash memory) which can electrically erase written data in a block is well known. Lately, there has been a tendency for a microcomputer to have a built-in nonvolatile memory as a substitute for the mask ROM or the RAM described above. If a nonvolatile memory is built into a microcomputer, due to the capability of nonvolatile memory to enable electrical erasing of written data, it will bring about an advantage that a program for operation control can be rewritten. Thus, cases in which a microcomputer has a built-in nonvolatile memory are increasing.
Microcomputers having a built-in memory of 8 bit data width were mainly used up until recently, but 16-bit type microcomputers have been developed most recently. Among the 16-bit type microcomputers, there is a microcomputer which uses two nonvolatile memories of 8 bit data width arranged in parallel as a single nonvolatile memory of 16 bit data width. In such a microcomputer, there is a case where data are rewritten into the nonvolatile memories on the microcomputer (self-writing).
However, usually in the microcomputer described above, unless the constitution of a microcomputer control section (microcomputer core) is changed to be applicable not to 8 bits, but to 16 bits, the 16 bit type microcomputer cannot be operated. The change of a microcomputer from 8-bit type to 16-bit type requires drastic improvement of the constitution of the microcomputer control section. Especially, program data for self-writing have to be changed drastically so as to be applicable to the 16-bits type microcomputer. Further, such improvement causes an increase of chip area or a fluctuation of circuit characteristics at the time of integration. Thus, a change of circuit is not that easy.